1. Field of the Invention
The present invention relates to a fluid supply system for supplying working fluid or lubricating oil to an operating device such as a transmission system, and more particularly to a fluid supply system in which a fluid passage for carrying the fluid or oil is formed through a rotating shaft.
2. Description of the Related Art
A power transmission device such as a transmission or a differential (a final reduction gear unit) is constituted by gears, clutches and bearings which are disposed on a rotating shaft which transmits a rotation driving force. And, lubricating oil for lubricating the gears, clutches and bearings, and clutch hydraulic operating fluid for operating the clutches are supplied to the gears, bearings and clutches through oil and fluid passages constituted by axial holes formed so as to axially extend in the rotating shaft. In the power transmission device, it is highly likely that metal friction particles generated from the gears, clutches, bearings, shaft and the like during the operation of the device enter and mix with the oil and fluid. In the event that the lubricating oil and hydraulic operating fluid containing the metal friction particles continue to be used as the lubricating oil and hydraulic operating fluid, there may be caused a risk that the abutment portions and contact portions of the gears, bearings and clutches are worn by the metal friction particle contained in the oil and fluid.
To cope with the problem, it is known that an oil filter having a filtering paper or a strainer having a metal screen is used to remove the dirt contained in lubricating oil or hydraulic operating fluid (for example, JP-A-6-159484 and JP-A-10-85523). Among the dirt contained in the oil or fluid, iron particles have the worst affect on the constituent components of the power transmission device, and therefore, a permanent magnet is often disposed within a transmission case, an oil tank, or an oil pan for the purpose of removing those iron particles. For example, the disposition of a permanent magnet at a drain plug is disclosed in JP-A-6-6896, JP-A8-303434, JP-A-11-290715.
By selecting filtering materials, the filtering accuracy of an oil filter and a strainer can be increased, but this causes problems that the higher the filtering accuracy, the higher the flow path resistance, that the production cost is increased, and that the power transmission device has to become large in size. In addition, the method of disposing the permanent magnet in the interior of the transmission case or the like makes the construction of the transmission device simple and reduces the production cost thereof, but all the oil and fluid do not always pass through in the vicinity of the permanent magnet, and therefore, there is caused a problem that the metal particle removing efficiency is reduced.
The invention was made in view of the above problems, and an object thereof is to provide a fluid supply system which is simple in construction and small in size and which can supply clean fluid by efficiently removing iron particles contained in the fluid.
With a view to attaining the object, according to the invention, there is provided a fluid supply system having a fluid supply source (for example, an oil container 21, a hydraulic pump P or a lubricating oil pump 77 in an embodiment of the invention), an operating device (for example, a transmission device 13 of a transmission 10, bearings 711, 71b, 78a, 78b of a final drive FD, differential clutches 75a, 756b or the like in the embodiment) receiving a fluid supply from the fluid supply source and a fluid supply passage (for example, lubricating oil supply tubes 22, 23, first and second axial holes 16a, 16b, a lubricating hole 17, first to fourth lubricating holes 84a to 84d, a fifth lubricating hole 80, lubricating portions 81a, 81b, sixth lubricating holes 82a, 82b, seventh lubricating holes 83a, 83b or the like in the embodiment) extending from the fluid supply source to the operating device. The fluid supply system further has a rotating shaft (for example, a transmission input shaft 15, a pinion gear 72 or an output shaft in the embodiment), and in the fluid supply system, a filtering member (for example, filtering members F, F1, F2 in the embodiment) is disposed which is formed into a cylindrical configuration and has a permanent magnet disposed within an axial hole (for example, a first axial hole 16a, the first lubricating hole 84a, or the lubricating portions 81a, 81b in the embodiment) formed so as to extend axially within the rotating shaft, and at least a part of the fluid supply passage is constituted by the axial hole within the rotating shaft and a cylindrical internal space formed within the filtering member.
Where the fluid supply system constructed as described above is used, as at least the part of the fluid supply passage is formed by the cylindrical internal space of the filtering member, all the fluid supplied from the fluid supply source to the operating device through the fluid supply passage passes through the cylindrical internal space of the filtering member, when iron particles are attracted by the permanent magnet constituting the filtering member so as to adhere thereto, whereby the iron particles are removed from the fluid in an efficient fashion. Furthermore, since the filtering member is disposed in the rotating shaft and rotates together with the rotating shaft, a centrifugal force produced when the rotating shaft rotates acts on the fluid passing through the cylindrical internal space of the filtering member. When this happens, since the specific gravity of the iron particles contained in the fluid is greater than that of the fluid, the iron particles on which the centrifugal force is acting are then caused to move toward an outer circumferential side of the space and hence to approach the permanent magnet and eventually adhere to the permanent magnet to thereby be removed in a more effective fashion.
Furthermore, it is preferable that the fluid supply system is constructed such that at least a pair of groove portions (for example, groove portions 33, 34, 44a, 44b, 54, 64a, 64b in the embodiment) is formed in a cylindrical inner surface of the filtering member in such a manner as to be positioned diametrically across a central axis of the filtering member and to extend in an axial direction, so that the magnetic flux of the permanent magnet converges in the pair of groove portions. According to this construction, the iron particles can be collected into the groove portions so as to adhere thereto for efficient removal from the fluid. Furthermore, it is preferable that downstream portions in a fluid flow direction of the pair of groove portions are dammed (for example, bent portions 39a, 49a in the embodiment) so as to form fluid reservoirs (for example, bag-like spaces 33a, 34a in the embodiment) on a downstream side of the groove portions. According to this construction, it is unlikely that the iron particles adhering to the interior of the groove portions formed into the fluid reservoirs are forced to separate therefrom by the flow of the fluid so as to flow thereout toward a downstream side of the flow, and moreover, since the flow of the fluid tends to stagnate in the fluid reservoir portions, the iron particles can be caused to adhere to the permanent magnet in a more effective fashion.
In addition, the invention may be constructed such that a rotating speed regulating means (for example, an engine in the embodiment) is provided for regulating the rotating speed of the rotating shaft, so that the rotating speed regulating means regulates the rotating speed of the rotating shaft in such a manner as to increase the rotating speed of the rotating shaft in response to an increase in volume of the fluid supplied from the fluid supply source (for example, the hydraulic pump P in the embodiment). Increasing the rotating speed of the rotating shaft increases the centrifugal force acting on the fluid flowing through the interior of the rotating shaft, and this causes the iron particles in the fluid to move toward the outer circumferential side of the rotating shaft so as to effectively adhere to the permanent magnet, thus the efficiency in removing the iron particles being improved. For this purpose, when there is supplied a large amount of fluid, the efficiency in removing iron particles may be improved by increasing the rotating speed of the rotating shaft to thereby offset the increment of fluid supply, whereby even in the event that the amount of fluid supplied is increased, a high iron particle removing efficiency can be obtained.